Process of improving aluminum alloys



'Iiatented Aug. 27, 1929.

" UNITED STA wrnnnnu sannnn, or ESSEN-BUHR, ennman ass'renon r ran 1mm 011' TH.

- GoLDscHmn'r A.-G., OF ESSEN, GERMANY.

PROCESS IMPROVING ALUMINUM ALLOYS.

No Drawing. Application filed January 19, 1 928, Serial No. 248,007, and in Germany January 20, 1927..

This invention relates to a process of improving aluminum alloys; and it comprises constituent and .in addition heavy metals may be present. In some alumi um alloys magnesium isreplaced by ma esium silicid; a substance which is very useful. In this type of aluminum alloys the relative proportion of the silicon is such as .to form the compound Mg Si withoutexcess ,of either magnesium or silicon. These allo. 5 containing magnesium silicid also have een im roved by the addition ,of heavy metals an particularly copper. In practlcal use however these copper-containing alloys are not all that can be desired. Increasing the copper content brings an increase in strength but lessens the suitability for cold and hot working. There'is a reduction in the expansion and an increased corrodibility. Lowering the 'copper' content to avoid these difficulties makesthe strength of the alloy too low.

In the prior Patent No. 1,656,502, January 17, 1928, whereon the present inventiorf is in some aspects an improvement, a particularly desirable alloy was described, this alloy carrying magnesium silicid,-1.2 per cent cop- .per and a little titanium. In the present invention an alloy of this type is employed. As the result of exhaustive, investigation of alloys of this type it is found that the best results areobtained with certain rather special ratios betweenthe alloying bodies and the aluminum and between these com onents themselves and a speciaL method 0 workin this alloy has been developed. With this composition and this method of working it is possiblenot only to secure maximum ten- Bile strength, elongation and suitability for ably increased.

hotiand cold working but also good resistance tofchemical ac'tion..

An alloy of the following composition.

Mg Si 1.5 per cent: 0.2 Copper 1.2 per cent 1 0.2 Titanium 0.5 per cent i 0.2

exhibits an extremely, good relationship between strength,.el0ngation, suitability for hot and cold working and resistance to corrosion. An addition of a slight amount of manganese still further improves the alloy; this giving an increase instrength and rendering the alloy insensitive to superheating. In the presence of the manganese it is not necessary to maintain an exact temperature in annealing between stages of working as with other alloys. The range of temperatures within which intermediate ahnealing can be successf3ull carried out is considers arule, 0.8 per cent of manganese, with a plus or minus variation of 0.3 er cent, gives the, best results. Wit this alloy, thebest method of work'- ing as yet devised in'obtaining good mechanical strength includes a preliminary mechanical Working, for example by rolling, drawing, pressing or forging. After this working the alloy is raised to 520 to 550 C. in

about half an hour, and then rapidly cooled,

cooling being followed by an ageing operamadeas to elongation and resistance to cor- A rosion, ithas been found beneficial to begin the ageing treatment at the high temperature after a preliminary rest at room temperature, this resting period following the cooling. A rest'period of 24 to 48 hours at room temperature is generally sufficient. After the resting perio the ageing at the high temperature is resorted to. In the 4 strengths can be imparted by interposing another mechanical working following the first high temperature treatment and the subsequent cooling. After this, the procedure is as before. Special results as regards strength, elongation, resistance to corrosion etc. can be obtained withvariationsin the described procedure consisting in using mechanical working at different stages in the operation, after annealing, after cooling, or after different time intervals prior to. the intermediate rest at room temperature.

Material of the stated composition treated in the stated manner gives a tensile strength of 37 to 54 kilograms per square millimeter with an elongation of 28 to 12 per cent. Corrosion tests show only about half the corrodibility of ordinary aluminum alloys. The material has excellent cold bending properties. Sheets and wires can be bent in an arc of very small radius. For example, a 4-millin'1eter sheet having a tensile strength of 41 kilograms per square millimeter can be'bent by hammering through 180 round a radius of 7 to 8 millimeters. This malleability is about double that of the known aluminum alloys 6f the sametensile strength. Not only is the malleability in the cold good but the malleability with a hot working is excellent. The present material can be easily pressed and drawn into thin tubes and complicated contours without requirement of frequent intermediate annealings and small intermediate stages of reduction. This fact gives great economy in the use of the present material.

Still higher-strengths, though with sacrifice of elongation, can be obtained by submitting the material to a final mechanical treatment.

YVhat I claim is I 1. In the improvement or alloyed alumi-v num containing 1.3 to'1.7 per cent magnesium silicid, 1 to 1.4 per cent copper,-and 0.3 to 0.7 per cent titanium, with or without 0.5 to 1.1 per cent manganese, the process 0.5 to 1.1 per cent manganese, the process which comprises mechanically working a body ofsaid alloy, heat treating at 520 to 550 (1., rapidly cooling and subsequently ageing at a temperature between-110 and 150 C. for 0 to 24' hours.

3. In the improvement of alloyed aluminum containing 1.3 to 1.7 per cent magnesium silicid, 1 to 1.4 per cent copper, and

0.3 to 0.7 per cent titanium, with or without 0.5 to 1.1 percent manganese, the process which comprises mechanically working a body of said alloy, heat treating at 520 to 550 (3., rapidly cooling and subsequently ageing at a temperature between 110 and 150 C. for 6 to 2 1 hours, the alloy body being allowedto rest for a time prior to 5 applying the ageing treatment.

WILHELM SANDER.

In testimony whereof I aflix my signature. v 

